{
 "version": "2026-10-20",
 "license": "Dimension sheets are written by Xem Studio from the cited sources and are free to use (CC BY 4.0, attribute 'Xem Studio'). Linked files belong to their publishers under the license shown; Xem Studio does not host them. 'license_verified: false' means the license shown is from memory or the publisher's page as last read and should be confirmed at the link before commercial use.",
 "slug": "thermoacoustic-stack",
 "name": "Thermoacoustic stack for tri-clamp spools: Ø34.8, Ø47.5 and Ø72.9, honeycomb and spiral",
 "kind": "hardware",
 "category": "Stirling engines",
 "group": "Thermoacoustic & fluidyne",
 "year": null,
 "question": "What size stack does a tri-clamp thermoacoustic engine need?",
 "tags": [
  "thermoacoustic",
  "stack",
  "honeycomb",
  "resonator",
  "tri-clamp",
  "stirling",
  "long earth society"
 ],
 "aliases": [
  "thermoacoustic engine stack",
  "thermoacoustic stack stl",
  "honeycomb stack",
  "thermoacoustic resonator length",
  "thermoacoustic refrigerator stack"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": true,
 "free_files": 11,
 "url": "https://xemstudio.com/objects/thermoacoustic-stack/",
 "sheet_txt": "https://xemstudio.com/objects/thermoacoustic-stack/sheet.txt",
 "sheet": {
  "basis": "Stack OD = 16 ga spool bore (34.8 / 47.5 / 72.9), exact; channel width 2–4 thermal penetration depths (δκ ≈ 0.26 mm in air at 1 bar, 100 Hz; 0.15 mm at 300 Hz), Swift",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "The stack is the core of a standing-wave thermoacoustic engine: many narrow parallel channels between a hot face and a cold face, sitting in the resonator tube. It is drawn at the spool bore, so it is held in the bore itself.",
   "Honeycomb stack (1.5 and 2 in, × 40): hexagonal cells 1.5 mm across flats with 0.4 mm walls, every cell whole inside a 0.4 mm outer ring. Spiral stack (all three sizes, × 30, 40 and 50): one 0.4 mm wall wound with a 1.0 mm gas gap from a Ø6 core to a 0.5 mm outer ring.",
   "Channel size: half-width 2–4 × δκ, δκ = √(κ / (π f ρ cp)), so about 1–1.5 mm channels at 100 Hz and about 1.0 mm at 300 Hz in air at 1 bar.",
   "Placement: centred about λ/8 from the closed (hot) end of a λ/4 resonator; a closed-open tube resonates at f = c / 4L (150 Hz → 572 mm, 300 Hz → 286 mm in air at 20 °C)."
  ],
  "table": {
   "columns": [
    "spool_in",
    "stack_od_mm",
    "forms",
    "lengths_mm",
    "quarter_wave_150hz_mm",
    "half_wave_150hz_mm"
   ],
   "rows": [
    [
     "1.5",
     34.8,
     "honeycomb 1.5 mm cells / spiral 1.0 mm gap",
     "40 / 30, 40, 50",
     572,
     1143
    ],
    [
     "2",
     47.5,
     "honeycomb 1.5 mm cells / spiral 1.0 mm gap",
     "40 / 30, 40, 50",
     572,
     1143
    ],
    [
     "3",
     72.9,
     "spiral 1.0 mm gap",
     "30, 40, 50",
     572,
     1143
    ]
   ]
  }
 },
 "sheet_text": "Thermoacoustic stack for tri-clamp spools: Ø34.8, Ø47.5 and Ø72.9, honeycomb and spiral — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/thermoacoustic-stack/  (CC BY 4.0)\nBasis: Stack OD = 16 ga spool bore (34.8 / 47.5 / 72.9), exact; channel width 2–4 thermal penetration depths (δκ ≈ 0.26 mm in air at 1 bar, 100 Hz; 0.15 mm at 300 Hz), Swift\nCatalog version: 2026-10-20\n\nSizes: see table below\n- The stack is the core of a standing-wave thermoacoustic engine: many narrow parallel channels between a hot face and a cold face, sitting in the resonator tube. It is drawn at the spool bore, so it is held in the bore itself.\n- Honeycomb stack (1.5 and 2 in, × 40): hexagonal cells 1.5 mm across flats with 0.4 mm walls, every cell whole inside a 0.4 mm outer ring. Spiral stack (all three sizes, × 30, 40 and 50): one 0.4 mm wall wound with a 1.0 mm gas gap from a Ø6 core to a 0.5 mm outer ring.\n- Channel size: half-width 2–4 × δκ, δκ = √(κ / (π f ρ cp)), so about 1–1.5 mm channels at 100 Hz and about 1.0 mm at 300 Hz in air at 1 bar.\n- Placement: centred about λ/8 from the closed (hot) end of a λ/4 resonator; a closed-open tube resonates at f = c / 4L (150 Hz → 572 mm, 300 Hz → 286 mm in air at 20 °C).\n\nspool_in  stack_od_mm  forms  lengths_mm  quarter_wave_150hz_mm  half_wave_150hz_mm\n1.5  34.8  honeycomb 1.5 mm cells / spiral 1.0 mm gap  40 / 30, 40, 50  572  1143\n2  47.5  honeycomb 1.5 mm cells / spiral 1.0 mm gap  40 / 30, 40, 50  572  1143\n3  72.9  spiral 1.0 mm gap  30, 40, 50  572  1143\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Wikipedia: Thermoacoustic heat engine — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Thermoacoustic_heat_engine\n- G. W. Swift (LANL): Thermoacoustics: A Unifying Perspective for Some Engines and Refrigerators (textbook; DeltaEC software free) — web, software — LANL [verify license at link] — https://www.lanl.gov/org/ddste/aldps/materials-physics-applications/condensed-matter-magnet-science/thermoacoustics/\n- NASA (NTRS, public domain): Thermoacoustic Stirling heat engine for space power — PDF — US Government work, public domain — https://ntrs.nasa.gov/search?q=thermoacoustic%20Stirling\n- Long Earth Society: Engine builds — web, video — LES site — https://longearthsociety.com/engineering/\n\nFree files (CC BY 4.0, Xem Studio; STEP + STL, 11 parts): https://xemstudio.com/files/hardware/thermoacoustic-stack/index.json\nAPI: https://xemstudio.com/api/geometry?object=thermoacoustic-stack\n",
 "sources": [
  {
   "publisher": "Wikipedia",
   "title": "Thermoacoustic heat engine",
   "url": "https://en.wikipedia.org/wiki/Thermoacoustic_heat_engine",
   "formats": [
    "web"
   ],
   "license": "CC BY-SA 4.0 (text)",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "G. W. Swift (LANL)",
   "title": "Thermoacoustics: A Unifying Perspective for Some Engines and Refrigerators (textbook; DeltaEC software free)",
   "url": "https://www.lanl.gov/org/ddste/aldps/materials-physics-applications/condensed-matter-magnet-science/thermoacoustics/",
   "formats": [
    "web",
    "software"
   ],
   "license": "LANL",
   "license_verified": false,
   "hosted": false
  },
  {
   "publisher": "NASA (NTRS, public domain)",
   "title": "Thermoacoustic Stirling heat engine for space power",
   "url": "https://ntrs.nasa.gov/search?q=thermoacoustic%20Stirling",
   "formats": [
    "PDF"
   ],
   "license": "US Government work, public domain",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Long Earth Society",
   "title": "Engine builds",
   "url": "https://longearthsociety.com/engineering/",
   "formats": [
    "web",
    "video"
   ],
   "license": "LES site",
   "license_verified": true,
   "hosted": false
  }
 ],
 "xem": {
  "status": "free-files",
  "sheet_free": true,
  "mesh_price_usd": null,
  "step_price_usd": null,
  "tolerance_mm": null
 },
 "related": [
  "thermoacoustic-heat-exchanger",
  "thermoacoustic-driver-cap",
  "tri-clamp-spool",
  "sanitary-clamp-spools",
  "stirling-configurations-guide"
 ],
 "fits": [
  {
   "role": "Goes in or on",
   "items": [
    {
     "slug": "tri-clamp-spool",
     "why": "stack OD = spool bore"
    }
   ]
  },
  {
   "role": "Connects to",
   "items": [
    {
     "slug": "thermoacoustic-heat-exchanger",
     "why": "hot and cold exchangers on the stack faces"
    },
    {
     "slug": "thermoacoustic-driver-cap",
     "why": "speaker cap closes the resonator"
    }
   ]
  },
  {
   "role": "Also needed",
   "items": [
    {
     "slug": "tri-clamp-end-cap",
     "why": "capped hot end"
    },
    {
     "slug": "tri-clamp-clamps",
     "why": "clamp per spool joint"
    }
   ]
  }
 ],
 "dimensions": "exact (nominal, no printing tolerance)",
 "dimension_rule": "All geometry on Xem Studio is exact (nominal, true size) with no printing tolerance. Where a part meets another part, the object lists its mating features (feature, exact size, what it mates with, fit class: press, slide, run, socket, clamp or designed). Apply your process's allowance to those features only; 'designed' gaps are part of the design and stay as drawn.",
 "mating": [
  {
   "feature": "stack OD",
   "exact": "spool bore (34.8 / 47.5 / 72.9)",
   "mates": "tri-clamp spool bore",
   "fit": "socket",
   "files": "stack-"
  }
 ],
 "fit_classes": {
  "press": "stays put: pin, tube, bearing or magnet held by interference. Typical FDM: hole +0.0 to +0.1 mm on diameter.",
  "slide": "assembles by hand and is held by a grub, pinch or clamp: shaft in a hub, rod in a socket, spigot in a bore. Typical FDM: +0.2 mm.",
  "run": "turns or slides in use: pin in a link, rod through a guide. Typical FDM: +0.3 mm.",
  "socket": "large sliding fit: syringe barrel, sleeve, bobbin in a bore. Typical FDM: +0.3 mm.",
  "clamp": "split part that closes on the mating part with screws: make it at size.",
  "designed": "a gap that is part of the design (piston fit option, displacer gap, air gap): do not change."
 },
 "faq": [
  {
   "q": "What channel size should a thermoacoustic stack have?",
   "a": "2–4 thermal penetration depths: about 1–1.5 mm in air at 1 bar and 100–300 Hz."
  },
  {
   "q": "How long should a thermoacoustic tube be?",
   "a": "Closed-open (λ/4): L = 343 / (4f): 286 mm for 300 Hz, 429 mm for 200 Hz, 858 mm for 100 Hz; closed-closed is twice that."
  },
  {
   "q": "Where does the stack go?",
   "a": "Centred about λ/8 from the closed hot end: 107 mm in a 429 mm (200 Hz) λ/4 tube."
  },
  {
   "q": "What diameter is the stack for a 2 inch spool?",
   "a": "Ø47.5, the 16 ga bore: a honeycomb stack × 40 or a spiral stack × 30, 40 or 50."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "stack-honeycomb-1.5in-40-c1.5",
   "formats": [
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    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/thermoacoustic-stacks-and-resonators/stack-honeycomb-1.5in-40-c1.5.step",
   "stl": "https://xemstudio.com/files/hardware/thermoacoustic-stacks-and-resonators/stack-honeycomb-1.5in-40-c1.5.stl",
   "note": "honeycomb stack Ø34.8 × 40 (the 1.5 in spool bore, exact): 1.5 mm hexagonal cells, 0.4 mm walls"
  },
  {
   "file": "stack-spiral-1.5in-30-g1.0",
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   "price_usd": 0,
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   "step": "https://xemstudio.com/files/hardware/thermoacoustic-stacks-and-resonators/stack-spiral-1.5in-30-g1.0.step",
   "stl": "https://xemstudio.com/files/hardware/thermoacoustic-stacks-and-resonators/stack-spiral-1.5in-30-g1.0.stl",
   "note": "spiral stack Ø34.8 × 30 (the 1.5 in spool bore, exact): one 0.4 mm wall wound with a 1.0 mm gas gap"
  },
  {
   "file": "stack-spiral-1.5in-40-g1.0",
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   "stl": "https://xemstudio.com/files/hardware/thermoacoustic-stacks-and-resonators/stack-spiral-1.5in-40-g1.0.stl",
   "note": "spiral stack Ø34.8 × 40 (the 1.5 in spool bore, exact): one 0.4 mm wall wound with a 1.0 mm gas gap"
  },
  {
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   "stl": "https://xemstudio.com/files/hardware/thermoacoustic-stacks-and-resonators/stack-spiral-1.5in-50-g1.0.stl",
   "note": "spiral stack Ø34.8 × 50 (the 1.5 in spool bore, exact): one 0.4 mm wall wound with a 1.0 mm gas gap"
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  {
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   "stl": "https://xemstudio.com/files/hardware/thermoacoustic-stacks-and-resonators/stack-honeycomb-2in-40-c1.5.stl",
   "note": "honeycomb stack Ø47.5 × 40 (the 2 in spool bore, exact): 1.5 mm hexagonal cells, 0.4 mm walls"
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   "stl": "https://xemstudio.com/files/hardware/thermoacoustic-stacks-and-resonators/stack-spiral-2in-30-g1.0.stl",
   "note": "spiral stack Ø47.5 × 30 (the 2 in spool bore, exact): one 0.4 mm wall wound with a 1.0 mm gas gap"
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   "stl": "https://xemstudio.com/files/hardware/thermoacoustic-stacks-and-resonators/stack-spiral-2in-40-g1.0.stl",
   "note": "spiral stack Ø47.5 × 40 (the 2 in spool bore, exact): one 0.4 mm wall wound with a 1.0 mm gas gap"
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   "stl": "https://xemstudio.com/files/hardware/thermoacoustic-stacks-and-resonators/stack-spiral-2in-50-g1.0.stl",
   "note": "spiral stack Ø47.5 × 50 (the 2 in spool bore, exact): one 0.4 mm wall wound with a 1.0 mm gas gap"
  },
  {
   "file": "stack-spiral-3in-30-g1.0",
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   "stl": "https://xemstudio.com/files/hardware/thermoacoustic-stacks-and-resonators/stack-spiral-3in-30-g1.0.stl",
   "note": "spiral stack Ø72.9 × 30 (the 3 in spool bore, exact): one 0.4 mm wall wound with a 1.0 mm gas gap"
  },
  {
   "file": "stack-spiral-3in-40-g1.0",
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   "stl": "https://xemstudio.com/files/hardware/thermoacoustic-stacks-and-resonators/stack-spiral-3in-40-g1.0.stl",
   "note": "spiral stack Ø72.9 × 40 (the 3 in spool bore, exact): one 0.4 mm wall wound with a 1.0 mm gas gap"
  },
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   "stl": "https://xemstudio.com/files/hardware/thermoacoustic-stacks-and-resonators/stack-spiral-3in-50-g1.0.stl",
   "note": "spiral stack Ø72.9 × 50 (the 3 in spool bore, exact): one 0.4 mm wall wound with a 1.0 mm gas gap"
  }
 ],
 "markdown": "https://xemstudio.com/objects/thermoacoustic-stack/index.md"
}